Jonathan, 11, likes to spend his vacations alone with his grandfather, who lives on the edge of a huge forest populated by strange animals. This year his kid sister Sophie (7) insists on joining him. But it's not cool to be stuck with a little sister, and so Jonathan does what he can to avoid her. He succeeds entirely too well: Sophie is kidnapped by a giant, thousand-year-old bear. Jonathan now has to venture into the heart of the forest to confront the strange beings that dwell there and rescue his sister.